Nowadays, there are several devices for taking samples of soft tissue, these devices being generally used to extract, in a minimally invasive way, a sample of an organ from a human being or an animal for analysis purpose. This extraction operation is generally known as biopsy and the device used is known as a biopsy gun.
Such a sampling device comprises, in particular, a sampling needle formed by a cannula and a stylet, an arming mechanism placed on a body and a trigger also placed on the body of the device.
The arming mechanism is used to partially retract the needle towards the inside of the body of the device. The device is placed near the organ from which a sample is to be taken, and then the trigger is pressed so that the needle can penetrate into the organ. The needle being formed by a stylet and by a cannula, the stylet penetrates into the organ, then the cannula covers the stylet. The stylet comprises at least one notch receiving the tissue sample to be taken. When the cannula covers the stylet, the tissue sample is trapped in the notch and is cut. The unit is withdrawn so that the sample(s) arranged between the stylet and the cannula can be removed. An example of application of such a device is taking tissue samples from the prostate.
The arming of the needle is generally achieved in two steps, namely the arming of the cannula in a first step and the arming of the stylet in a second step.
During sampling of tissues, it is common for the person carrying out the sampling to have only one free hand, while the other hand is being used to hold other medical devices, such as for example an echographic probe. In this case, it is important to be able to handle the sampling device with one single hand. Here, the handling includes the arming of the cannula, the arming of the stylet and the release of the shot allowing the sample to be taken.
An example of existing devices, which enable handling with one single hand, is described in U.S. Pat. No. 7,153,275. This device is perfectly functional in most cases. However, problems may occur in certain circumstances. These problems may arise from the fact that the stylet and the cannula are not perfectly aligned and the stylet does not slide in a totally optimal way in the cannula. Indeed, an optimal sliding motion involves particularly tight manufacturing tolerances when manufacturing the parts of the biopsy gun. These tolerances can sometimes be difficult to maintain on parts made from plastic. This may lead to jamming of the needle, sometimes even deformation. A further consequence is the reduction in the number of shots that can be carried out with a device.
In order to minimize the problems linked to the jamming of the stylet in the cannula, a relatively powerful spring is used for the cannula in order to propel the latter in an effective way. This has the drawback that a greater force is required to arm the device, which is undesirable for the user. Despite such a spring, the needle may jam and bend so that the device becomes unusable.
The following description describes a tissue sampling device which has the advantages of the devices of the prior art, i.e. it is possible to use this device with one hand. However, this device does not have the drawbacks of the systems of the prior art. Thus, the risk of jamming of the needle, as well as the risk of breakage or deformation, is strongly reduced or even eliminated.